## Arihangdu one year ago How to calculate oxidation number of chlorine in Al(ClO4)3

1. Zale101

What is the overall charge of perchlorate?

2. Arihangdu

I don't know?

3. Zale101

the overall charge of perchlorate is -1

4. Zale101

what about oxygen, what is the charge of it?

5. Arihangdu

-2

6. Zale101

Correct. How many oxygen atoms are there?

7. Arihangdu

12

8. Arihangdu

4 x 3=12 right

9. Arihangdu

- 2 right or 7

10. Arihangdu

3

11. Arihangdu

Questions is what is the oxidation number of in Al(ClO4)3 ?

12. Zale101

Correct. So Oxygen has 12 atoms and -2 charge Chlorine has 3 atoms. Al has a charge of +3 and it has only one atom The overall charge of a compound has to equal to zero. That means, the information that we know can be applied as $$+3+3\color{red}{x}+(-2)(12)=0$$ The x in red means that we don't know the charge of chlorine but we know it has 3 atoms.

13. Zale101

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14. Arihangdu

Value of x is chlorine fight?

15. Zale101

The value of x is the chlorine's oxidation number.

16. Arihangdu

3 X =_21, x= -7?

17. Zale101

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18. whpalmer4

A shortcut would be to note that if we have $$\text{Al}^{3+}$$ and 3 perchlorate ions, each one of the perchlorate ions must have a net charge of $$-1$$. Knowing that the oxygen atoms each have a charge of $$-2$$, $-1 = Cl + 4 * O$$-1 = Cl + 4*(-2)$$-1 = Cl -8$$7 = Cl$ so our chlorine oxidation number is +7.